Serco, which has run the London to Scotland service since 2015, racked up a £3.3m loss, despite receiving £23m in subsidies from Transport Scotland, according to accounts filed last week.

The financial statements also reveal that from 2022, Serco has the right “to seek adjustments to the financial terms of the franchise agreement that would result in either a small positive profit margin for the company from that date, or allow us to exit the contract”.